Cover for an outdoor tank

ABSTRACT

The invention relates to a cover for an outdoor tank, the cover being made of a plate that can be treaded on and shifted between an open and a closed position, wherein the cover is guided displaceably on rails for opening and closing purposes in an at least approximately parallel fashion to the opening surface of the tank. A seal acting between the cover and the edge surface of the tank is brought into contact with the corresponding surface during the closing motion by such a relative movement that has a clear directional component, said directional component being normal on and directed toward said surface. The temperature of the surface from which the seal is removed when the cover is opened is automatically monitored and automatically raised by a heating element when the temperature falls below the freezing point.

The invention relates to a movable rigid cover for an outdoor tank, forexample a swimming pool.

DE 297 09 674 U1 discloses a cover, in particular for swimming pools,formed from at least one rigid, flat board which is designed to be movedvia rollers on rails. In the form described therein, the board consistsof Plexiglas; between the edge of the swimming pool and the board thereextends a brush seal. When the swimming pool is open, the board isretracted under a cover arranged next to the swimming pool. This coverprotects and covers the board and the rail region on which it is moved.

A disadvantage of this type of construction is that, primarily in cool,sunless weather, a great deal of heat can be lost even from the coveredswimming pool, because in that case the amount of heat introducedthrough the Plexiglas is much less than the amount of heat lost throughheat flux. The brush seal is highly mechanically loaded by the relativetangential movement of the board with respect to the edge of theswimming pool and when it is detached at sub-zero temperatures, and israpidly destroyed. All kinds of leaves, earth and pests rapidly gatherin the cavity beneath the cover. It is difficult and time-consuming tokeep this cavity clean.

DE 2005 009 842 U1 discloses a swimming pool cover which is made of aflat board, can be walked on and can be moved on rails. The cover ispreferably arranged in a plane with a surrounding terrace area andcovered with the same covering. The rails are arranged in depressions inor on the terrace area. The proposed design appears optimized such thatthe swimming pool is emptied and covered over in the colder half of theyear but the terrace area can still be used. There is no discussionregarding the problem of heat loss from the swimming pool and themovability of the cover even in snowy conditions.

The object of the invention is to improve the cover according to thedescribed prior art for an outdoor tank, typically a swimming pool,which cover consists of a flat board which can be walked on and can bemoved on rails, such that even when it is snowy and cold it can beopened and closed easily and without damage and such that the heat lossfrom the tank is minimized.

One or more of the following improvements are carried out in order toachieve the object with respect to the type of construction inaccordance with the prior art:

-   -   The seals which act, when the cover is completely closed,        between the latter and the edge of the tank are moved, with that        part (tank edge or cover) against which they come to bear during        the closing process, by such a relative movement toward this        part, which movement has a large normal component to the surface        of this part against which the seals are brought into abutment.        When the cover is opened the reverse sequence takes place. That        is to say, first the seals are disengaged by a movement with a        large normal component to the sealing surface to be opened and        only then is the cover pushed away.    -   The advantage achieved thereby is that damaging sliding movement        between the seal and the surface toward which the seal must be        brought during the closing process or from which it must be        separated during the opening process is avoided.    -   The surfaces from which the seals must be detached when the        cover is opened are automatically heated by a frost monitor.    -   This prevents the seals from freezing solid. Seals that seal        very well but are otherwise mechanically sensitive and made of        flexible plastics can thus be used.    -   Rails on which the movement of the cover is guided during        opening and closing and also the surface region between the        rails which is located next to the tank are freed of ice and        snow or are permanently kept free thereof, as required, by        integrated heating.    -   The result of this is that the cover can also be opened and        closed as required in winter without problems.

The invention, further details relating thereto and practicaldevelopments are described with the aid of drawings which show anadvantageous embodiment of the invention in somewhat stylized form:

FIG. 1: is a vertical sectional view of an embodiment of the inventionin the application as a whirlpool. The cover has been opened about halfway. For reasons of clarity the earth is assumed to be transparent andnot, as is otherwise conventional for sectional planes, shown ashatched.

FIG. 2: shows the arrangement in FIG. 1 from above.

The cover 1 is a rigid, flat and horizontally arranged board. In anadvantageous embodiment it is formed from a stainless steel frame whichis filled or lined with a thermally insulating material. On its top itis provided with a ground covering in line with the customer's wishes,for example with wooden planking. On its underside the cover 1 isprovided with wheels 3 which roll on a pair of stationary rails 4. Thetwo rails 4 run parallel to one another on either side of the tank to becovered 5, over its entire length.

The movement of the board can be driven in a very convenient embodimentby way of electric motors, which drive the wheels 3 and can be switchedon and off remotely. By omitting components, simpler embodiments of thisembodiment can be created, right down to the one in which the cover 1 issimply pushed by hand. In embodiments driven by a motor, for safetyreasons a stop sensor should be provided which, starting at a particularresistance, either switches off the drive or switches to movement in theopposite direction when an obstacle is encountered.

A seal 2 is mounted at the edge of the lower surface of the cover 1,which seal bears with its side facing away from the cover 1 against theedge 5.1 of the tank to be covered when the cover is closed. Accordingto the invention, there is provision to make the edge 5.1 heatable, inthe region of that surface part against which the seal 2 bears, by meansof a heating device, for example an electric heating wire arranged justunder the surface, and to monitor the temperature at this surface regionusing sensors. By means of the heating device, the temperature of thissurface part is then kept at least just above freezing point.

In order that the seal 2 is not stressed at the surface 5.1 by beingpulled in a direction tangential to the surface 5.1, it is only movedtoward the surface 5.1 at the end of the closing movement of the coverby a relative movement with respect to the surface 5.1, which movementhas a substantial component normal to the surface 5.1. In theillustrated example, this is brought about by the stepped design of therails 4. In most of the longitudinal region of the rails the rollingsurface for the wheels 3 of the cover 1 is aligned parallel to thesurface 5.1 and arranged at such a level that the seal 2 attached to thecover is raised so far above the surface 5.1 that it does not touch thelatter. Only in that longitudinal region of the rails 4 at which thewheels 3 are located when the cover 1 is closed is the rolling surfaceof the rails lowered with respect to the surface 5.1 to such an extentthat the seal 2 bears against the surface 5.1. The transitions betweenthe raised and the lowered parts of the rolling surface on the rails areformed as relatively short, that is to say steep ramps 4.1. When thecover is closed, the cover only drops down in the very last part of theclosing movement, that is to say a movement of the cover toward thesurface 5.1, which movement has a substantial component in the directionnormal to the surface 5.1.

The approaching movement of the seal to the surface 5.1 with asubstantial directional component normal to the surface 5.1 can ofcourse also be brought about by means other than a curved rollingsurface on the rails. The seal itself can be moved relative to the covertoward the countersurface on the tank edge once the cover has beenpushed over the tank into the closed position. By way of example, theseal may for this purpose be attached to a profiled bar mounted on thecover such that it can rotate in its profile plane. For closing, theprofiled rod is rotated such that the seal bears against the edgesurface of the tank. For opening, the profiled bar is moved away fromsaid surface again. It is of course also possible to attach the seal toa bar which is moved normal to its longitudinal direction linearlytoward the corresponding surface of the tank edge.

In order that the opening and closing movements of the cover are notimpeded by ice or snow, the rails 4 and the surface region 10 betweenthe two rails that is located next to the tank are also provided with aheating device by means of which ice and snow can be melted as required.For the rails, this heating device may in turn consist, for example, ofan electric heating wire or of an electric heating film arrangedthereon. For the surface region 10, conventional undersoil heatingsystems based on hose loops through which a heat-transfer medium flowscan be provided.

A typical whirlpool is a tank filled with water, the wall surfaces ofwhich are formed such that the users are provided with seating formedsuch that, when they sit on it, only their head protrudes from the waterand they are massaged by jets of water and/or blown-in air from amultiplicity of nozzles. The water is heated to a comfortabletemperature. It is conventional to treat the water by means of filtersand chemical treatment, for example by means of ozone, continuously suchthat it does not need to be changed for a relatively long time, forexample a year.

The structure according to FIG. 1 and FIG. 2 is advantageous primarilyfor heated outdoor whirlpools that can be used throughout the year.

An outer tank 5 is mounted supported on a foundation and surrounded byearth. In an embodiment which is advantageous because it is durable, itssurfaces are constructed in the manner of a sandwich from in each caseone external stainless steel sheet and an insulating layer spanning theinterspace, made for example of PU foam. The actual whirlpool 6 isinstalled in this tank 5. The whirlpool does not cover the entire innerarea of the tank, rather free space 7 remains in the tank 5, from whichspace necessary maintenance work on the whirlpool 6 or on additionalappliances mounted thereon can be carried out if appropriate. Inaddition, the tank 5 still has the very important function of thermalinsulation between the outside of the whirlpool 6 and the surroundingearth. When the cover is closed the space in the tank 5 is closed off inan airtight manner from the external air by the seal 3, which then bearsagainst the edge 5.1 of the tank. The tank 5 considerably simplifies theinstallation sequence compared to the conventional type of constructionin which the walls of the depression required for sinking the whirlpoolhave to be concreted in the earth.

In order that the whirlpool can be used at any time without a long leadtime, the water contained therein is kept warm constantly. In order thatthe heat loss during those times in which the whirlpool is not beingused and the cover 1 is closed is kept as low as possible, an additionalthermally insulating layer 8 is arranged on the underside of the cover 1in that region located directly over the whirlpool, which layer, whenthe cover is closed, bears either directly or by way of acircumferential soft seal against the upper edge of the whirlpool. Whenthe insulating layer 8 bears directly against the whirlpool, it shouldbe made from a flexibly resilient material, for example a resilientplastic foam, at least in the region where it touches the whirlpool. Thesame considerations as above for the seal 2 between the cover and theedge 5.1 of the outer tank 5 apply for the movement of the cover duringclosing and opening with respect to this seal arrangement.

In order to enable simple visual monitoring of the whirlpool, in anadvantageous embodiment the cover 1 and the insulating layer 8 locatedthereunder are provided with an opening penetrating both surfaces, whichopening is closed by a highly thermally insulating tread-resistantinsulating glass panel 9.

1. A cover for an outdoor tank, which cover consists of a board, can bewalked on and can be moved between an open and a closed position,wherein, in order to open or close the cover, the latter can be movedguided on rails at least approximately parallel to the opening surfaceof the tank, wherein a seal is attached to one of the two parts, coveror edge surface, of the tank, irrespective of whether the cover is openor closed, and comes into contact with a sealing surface at the secondpart when the cover is closed and is released therefrom when the coveris opened, characterized in that, during the closing process, the sealis brought into contact at said second part by such a relative movementwith respect to the surface, which movement has a clear directionalcomponent which is normal to this surface and is directed toward thelatter, and in that the temperature of that surface from which the sealis released when the cover is opened is monitored automatically by atemperature sensor and is raised automatically by a heating devicearranged in the vicinity if the temperature falls below freezing point.2. The cover as claimed in claim 1, characterized in that the rails onwhich the movement of the cover is guided during opening and closing areheated by a heating device arranged in their vicinity.
 3. The cover asclaimed in claim 1, characterized in that the surface region between therails which is located next to the tank is heated by a heating devicearranged thereabove or therebelow.
 4. The cover as claimed in claim 1,characterized in that the cover is provided with rotatable rollers bymeans of which it rests on stationary rails such that it can travel,wherein those longitudinal regions of the rails on which the rollers liewhen the cover is closed are lower than the adjacent longitudinalregions of the rails, directed toward the tank bottom, in the directionof the opening movement.
 5. The cover as claimed in claim 1,characterized in that the seal is attached to a profiled bar which ismounted such that it can rotate about an axis parallel to itslongitudinal direction.
 6. The cover s claimed in claim 1, characterizedin that the seal is attached to a profiled bar mounted such that it canmove linearly parallel to its profile plane.
 7. The cover as claimed inclaim 1, characterized in that it extends over an outer tank in which asmaller inner tank is arranged, wherein only the inner tank is filledwith water, wherein the surfaces of the outer tank are designed to bethermally insulating and wherein at least one horizontal externaldimension of the inner tank is much smaller than the horizontal internaldimension of the outer tank in the same direction.
 8. The cover asclaimed in claim 7, characterized in that it is provided on itsunderside, in that surface region which is over the inner tank when thecover is closed, with an additional thermally insulating layer comparedwith other surface regions of the cover, which additional layer rests onthe edge of the inner tank directly or by way of a seal when the coveris closed.
 9. The cover as claimed in claim 7, characterized in that itis provided, in the region of that surface which is over the inner tankwhen the cover is closed, with an opening closed by a tread-resistantinsulating glass panel.
 10. The cover as claimed in claim 7,characterized in that the inner tank is a whirlpool.